SCAFFOLDS Fruit Journal, Geneva, NY Volume 4 Update on Pest Management and Crop Development May 30, 1995
43F 50F Current DD accumulations (Geneva 1/1-5/30): 648 340 (Highland 3/1-5/29): 668 336 Coming Events: Ranges: Spotted tentiform leafminer sap-feeders present 295-628 146-325 Plum curculio oviposition 448-670 232-348 Spotted tentiform leafminer 1st flight subsides 489-978 270-575 Redbanded leafroller 1st flight subsides 518-893 255-562 American plum borer 1st flight peak 535-962 273-601 Codling moth 1st flight peak 547-1326 307-824 Peachtree borer 1st catch 565-1557 299-988 San Jose scale 1st flight peak 581-761 308-449 Obliquebanded leafroller pupae present 612-860 330-509 PHENOLOGIES: Geneva, 5/30 Apple (McIntosh): Fruit Set Pear: (Red Delicious): Petal Fall TRAP CATCHES (Number/trap/day) Geneva: 5/15 5/17 5/22 5/25 5/30 Green Fruitworm 0.3 0 0 0 0 Redbanded Leafroller 2.0 1.3 1.3 1.0 0.2 Spotted Tentiform Leafminer 492 812 202 108 63 Oriental Fruit Moth (apple) 57.0 71.0 10.9 9.5 2.1 Lesser Appleworm 28.9 14.0 12.2 15.0 6.9 Codling Moth - 6.0* 2.3 3.7 1.9 San Jose Scale 0.1* 0 0.1 1.0 0 American Plum Borer (cherry) 0.1* 1.0 0.4 1.8 0.8 Lesser Peachtree Borer (peach) - - 0 0.3* 1.1 Lesser Peachtree Borer (cherry) - - 0 0 0.6* Highland (Dick Straub, Peter Jentsch) 5/8 5/15 5/22 5/29 Green Fruitworm 0 0 0 0 Redbanded Leafroller 0.8 0.7 0.6 <0.1 Spotted Tentiform Leafminer 6.0 8.2 2.6 0.5 Oriental Fruit Moth 0.8 1.0 0 0.5 Fruittree Leafroller 0.1* 0.2 0 0 White Apple Leafhopper nymphs 0.1* <0.1 - <0.1 Codling Moth - <0.1* 1.9 4.6 Lesser Appleworm - - 1.0* <0.1 Sparganothis Fruitworm - - 0 0 Tufted Apple Budmoth - - <0.1* 1.1 * = 1st catch PEST FOCUS Geneva: Lesser Peachtree Borer 1st catch, 5/25 Highland: 1st Plum Curculio oviposition scars in apples, 5/23; 1st Rose Leafhopper on floribunda rose.
A description of the disorder and the origin of the term "scarf skin" dates back to the 1905 publication of "The Apples of New York" by Beach et al. They described scarf skin as "a dull or clouded appearance to the red skin as in 'Sweet Winesap' or 'Black Gilliflower'". Researchers have since shown that the disorder occurs when the epidermis and cuticle separate from the underlying tissue. The resulting air space beneath the waxy fruit surface disrupts light transmission and produces the milky or cloudy appearance. Unfortunately, we still do not understand what causes scarf skin to develop. Various researchers have noted that scarf skin is consistently more severe in some orchard blocks than in others. We also know that some cultivars are more susceptible than others and that the problem is more severe in some seasons than in others.
Scarf skin was studied by Dr. David Ferree and coworkers in Ohio in the early 1980's (see the two articles cited below). By bagging 'Rome Beauty' fruit clusters in polyethylene bags at various times beginning at petal fall, they were able to demonstrate that scarf skin is initiated between petal fall and 60 days after petal fall. Fruit bagged for 60 days had no scarf skin. The greatest amount of scarf skin was initiated close to petal fall, and the severity of scarf skin from later exposures decreased gradually. Fruit protected for 40 days showed very little scarf skin. Severity of scarf skin was not affected by applications of Solubor, calcium chloride, or dimethoate, but it was reduced by applications of giberellic acid (GA4+7).
Ferree and coworkers also showed that scarf skin was significantly more severe on trees receiving a seasonal program of Benlate or Dikar fungicides than on trees sprayed with Polyram, Dodine, Captan, or mancozeb. However, these fungicides do not consistently cause a scarf skin problem. Other researchers have compared various fungicides for their impact on scarf skin and have found that, in some seasons and some orchards, Benlate and Dikar had no deleterious effects. Nevertheless, the work by Ferree and observations that I have made in New York both support the hypothesis that Benlate applied within 40 days of petal fall can contribute to development of scarf skin in some years. (No other fungicide appears to stimulate scarf skin as frequently or as severely as does Benlate.) The effect of Benlate is probably dependent on interactions with environmental and possibly nutritional conditions at critical periods in the development of the fruit.
The period of greatest mechanical stress at the surface of rapidly growing apple fruits occurs as fruit reach approximately one inch in diameter, and this period coincides with the period of high susceptibility to both scarf skin and russet. Probably any factors that contribute to stressing the fruit during this critical period may promote scarf skin development. Various researchers have shown that environmental conditions during the 40 days after bloom are important in determining the amount of scarf skin that will develop, but the exact weather conditions that contribute to scarf skin have not been defined. Ferree et al. suggest that climatic changes that stress fruit during the critical period after petal fall may contribute to scarf skin. Thus, a period of cool, rainy weather followed by a hot, sunny, windy day might constitute a stress that could cause the separation in cell layers that results in scarf skin. An application of Benlate during this critical time might decrease elasticity of the cells on the fruit surface and thereby contribute further to the problem, whereas Benlate applications under other conditions may have no adverse effects. Given the current state of our knowledge (or lack thereof), we cannot provide recommendations that ensure scarf skin will not appear. We can only suggest that growers concerned about this problem avoid using Benlate during the 40 days after petal fall and, if possible, irrigate trees as needed to minimize water stress during this same critical period of fruit development.
Published information on scarf skin:
Apropos of which, Harvey Reissig's chemical control trials against OBLR in two Orleans Co. orchards last year generated some noteworthy results. He tested two basic spray timings using Lorsban: 2 applications, starting on July 7 (640 DD base 50F after the first adult catch) and July 22; and 3 applications, starting June 20, estimated to coincide with first hatch of the summer larvae, plus July 7 and July 22. The 3-spray program was also conducted using Asana and Guthion. The conclusive results showed the best control was obtained with the Asana program. The 2- and 3-spray programs of Lorsban were equally effective. Lorsban was more effective than Guthion in only one orchard, the one with moderate OBLR pressure (4.3% fruit damage in the check; the other had 36.3% fruit damage). These results indicate that the OBLR in these two orchards are almost as resistant to Lorsban as they are to Guthion, which has been considered ineffective for many years.
What does this mean to the average grower? First of all, these orchards should not necessarily be considered as representative of all commercial blocks in the state. We traditionally go to the worst trouble spots for these trials, and there are undoubtedly many orchards where Lorsban will still provide acceptable control of this pest. (Even Penncap-M still works pretty well in some spots, so you should be the expert regarding the activity of various products on your own farm.) However, the message from these trials is that this insect's inevitable march towards resistance to the commonly used materials is indeed proceeding, as we have feared. It so happens that the once-pronounced resistance OBLR showed to pyrethroids appears to have subsided somewhat for the time being, and it may be possible to squeeze a couple of years' worth of control out of an Asana program before it resurfaces. Naturally, we make this statement with the appropriate cautions about its potentially detrimental effects on mite control programs, but in this case there simply is no easy way out.
The good news is that in all likelihood, by the time Asana's effectiveness begins to flag once again, we will probably have registrations for some of the new insect growth regulator compounds currently rounding the regulatory bend for OBLR control. These include Comply (fenoxycarb) and Confirm (tebufenozide), both of which promise quite good activity on our favorite enemy. In the meantime, in sites where Lorsban has been showing signs of diminished capacity, use it only at petal fall in order to decrease selection pressure on the summer generation, against which you should elect either Asana or a short-interval (weekly) 4-5-spray low-rate B.t. program.
SJS infestations on the bark contribute to an overall decline in tree vigor, growth, and productivity. Fruit feeding causes distinct red-purple spots that decrease the cosmetic appeal of the fruit. Control measures for SJS are recommended when the scale or their feeding blemishes have been found on fruit at harvest during the previous season. Insecticidal sprays are most effective when directed against the first generation crawlers, specifically timed for the first and peak crawler activity, which are usually 7-10 days apart. The most reliable method of determining first appearance of the crawlers in your specific area is by putting sticky-tape traps on the tree limb near encrusted areas and checking them at least twice a week, starting next week. Alternatively, a degree-day accumulation of 310 (50 F base) from the date of first adult catch has also been shown to be reliable if the degree-days are known with some accuracy.
Effective materials for SJS control include Lorsban 50WP, Guthion, Imidan and Penncap-M. These sprays may also help in the control of OBLR, apple maggot, and codling moth. Coverage and control are generally better if the pesticide is applied dilute and in every row. SJS is frequently a problem in larger, poorly pruned standard size trees that do not receive adequate spray coverage. Dormant or delayed-dormant sprays of oil, or 1/2-inch green applications of Lorsban 4EC or Supracide will help prevent populations from getting established. Early season pruning is important for removing infested branches and suckers, as well as for opening up the canopy to allow better coverage in the tree tops where SJS are often concentrated.
By:Dave Kain and Art Agnello, Entomology, Geneva
Some of the most frequent comments and questions put to us over the course of the season during a given year, particularly during the first part of the season, have to do with "how we're doing" on pest and tree development in comparison with last year, or with a "normal" year. Naturally, although some of this is only idle curiosity, sometimes a few good clues about the season can be gathered by comparing the relative timings of yearly events -- are the trees ahead of the insects, are some pests out of sync with the season while others aren't, is everything behind schedule? We don't pretend to possess any startling insight about how things are going this year, but we thought it might be worthwhile to provide some comparative listings of a few noteworthy events this year, as well as for 1994 and for the calculated "normal" occurrence, based on however many observations we have on record. The following Progression Of Events gives degree-day values for some arbitrarily selected happenings:
Normal 1994 1995 DD (base 43F) accumulation to date (5/30): 691 557 648 Pear Psylla 1st oviposition 80 49 111 Pear Psylla 1st nymphs present 242 257 236 Green Fruitworm peak flight 134 118 230 European Red Mite hatch begins 284 257 290 Redbanded Leafroller 1st flight peak 298 ND 406 Spotted Tentiform Leafminer 1st flight peak 308 372 439 Oriental Fruit Moth 1st flight peak 428 372 439 Codling Moth 1st catch 484 450 439 Lesser Peachtree Borer 1st catch 589 581 563 McIntosh at full bloom 377 372 406 McIntosh at petal fall 484 450 563
Scaffolds is published weekly from March to September by Cornell University -- NYS Agricultural Experiment Station (Geneva), and Ithaca -- with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:
Scaffolds Fruit Journal
Editors: A. Agnello, D. Kain
Dept. of Entomology, NYSAES
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX:315-787-2326
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